The development of hydrogen and/or deuterium generation sources for laser fuels has obviated the need for high pressure storage facilities under cryogenic conditions.
After the development of hydrogen and/or deuterium generation sources for high purity laser fuels, the needs were recognized for additional improvements such as chemical reactants capable of generating hydrogen or deuterium in higher yield and with higher purity as evidenced by the evolution of the art described below.
Compositions which generate hydrogen are disclosed in U.S. Pat. No. 3,666,672, "Hydrogen Generating Compositions", by Ralph H. Hiltz. Disclosed is an autogeneously combustible composition that liberates hydrogen on burning The composition contains an alkali metal borohydride and a hydrazine sulfate in proportions such that there are between about 0.5 to 2 boron atoms for each nitrogen atom.
Another example of a prior art source for hydrogen generation is disclosed by Huskins et al in U.S. Pat. No. 3,940,474 wherein unsolvated aluminum hydride is decomposed by a heat source (e.g., a wire of about 80% nickel and 20% chromium with a predetermined diameter which is positioned in contact with the unsolvated aluminum hydride, and provided with a means for electrically heating the hydride to a decomposition temperature range from about 180.degree. C. to about 185.degree. C.) to provide hydrogen gas at a lower temperature.
Examples of prior art compositions for producing hydrogen or deuterium at about 600.degree. C.-700.degree. C. are disclosed by Ayers et al in U.S. Pat. No. 3,948,699. These compositions are based on complex metal boron compounds of the general formula M(BH.sub.4)x or M(BD.sub.4).sub.x, (wherein M equals a metal and x equals the valence of the metal M; M is an alkali metal or an alkali earth metal; H is hydrogen, and D is deuterium) and metal oxides of the general formula Q.sub.2 O.sub.3 (wherein Q is a trivalent metal selected from iron, aluminum, gallium, cobalt, and indium) combined stoichiometrically.
Higher temperature hydrogen or deuterium (e.g., about 3000.degree. C.) production is disclosed by Ayers et al in U.S. Pat. No. 3,948,700. This patent discloses a storable solid propellant composition based on unsolvated aluminum hydride and ferric oxide which produces high temperture gases from a self-sustaining reaction, once started, by a heat source such as an electrically heated nickel-chromium ignition wire. The hydrogen or deuterium produced is acceptable for use in HF/DF and HCl chemical lasers, the gas dynamic laser (GDL), or a source of hot gases for reducing fuel.
Additional prior art is disclosed by Chew et al in U.S. Pat. No. 4,061,512 which relates to storable solid propellant compositions based on complex metal boron compounds of the general formula M(BH.sub.4).sub.x or M(BD.sub.4).sub.x (wherein M equals a metal and x equals the valence of the metal M; M is an alkaline metal or an alkaline earth metal; H is hydrogen, and D is deuterium) and ammonium salts of the general formula (N H.sub.4).sub.n Y or deuteroammonium salts of the general formula (N D.sub.4).sub.n Y (wherein Y represents an anion with a total charge of n; N is nitrogen, H is hydrogen and D is deuterium. The specified compounds combined stoichiometrically or in varying molar ratios produce hydrogen or deuterium that contains nitrogen as an inert diluent which is acceptable for use in HF/DF chemical lasers, the gas dynamic laser GDL, or as a source of hydrogen containing an inert diluent.
In recent disclosures by Chew et al in U.S. Pat. No. 4,157,927, a class of compounds known as amine boranes and their derivatives are mixed with heat producing compounds such as lithium aluminum hydride or a mixture, such as NaBH.sub.4 /Fe.sub.2 O.sub.3 mixtures combined in definite proportions in a mixer or ball mill to produce a uniformly mixed powder. The mixed powder is then pressed into pellets and ignited to produce the hydrogen or deuterium as well as byproducts that are non-deactivating diluents. The oxide/borohydride or oxide/aluminohydride combination provides the thermal energy for decomposition of the amine borane.
In the further advancement of hydrogen and/or deuterium generation sources Grant et al in U.S. Pat. No. 4,381,206 disclosed an all amine borane gas generating system which consists of hydrazine bis-borane or its deuterated derivative in the form of a compacted solid propellant pellet which serves as the thermal stimulus for the decomposition of itself. An all amine borane gas generating system which additionally consists of diborane diammoniate or its deuterated derivative provides a higher yield of hydrogen or deuterium with a higher purity from a self-sustaining reaction after the self-sustaining reaction is initiated by a heat source (e.g., an electrially heated nichrome wire) sufficient to initiate the reaction. This all amine borane gas generating system which consists of N.sub.2 H.sub.4.2BH.sub.3 and H.sub.2 B(NH.sub.3).sub.2 BH.sub.4 is in the form of a compacted solid propellant pellet. The pellets are formed to the desired configuration employing pressures from about 500 to about 10,000 pounds total load. The solid propellant pellets are useful as a H.sub.2 or D.sub.2 generation sources for fuels for lasers.
Gas generator formulations of the prior art have provided yields in the range of 16 weight percent and exceeding 99 percent purity; however, because of inadequate thermal stability for Army field application, a lower yield such as exceeding 12.5 weight percent with improved thermal stabilities are proper trade-off considerations.
Therefore, an object of this invention is to provide thermally stable, solid reactant hydrogen and/or deuterium gas generator formulations which yield greater than 12.5 weight percent H.sub.2 or D.sub.2.
Another object of this invention is to provide a gas generator formulation which can be formed into reactant pellets having good physical properties in addition to having good thermal stability properties for field applications.